The present invention relates to a pressure control valve, in particular an electrically operable multi-way valve for hydraulic automotive vehicle brake systems with wheel slip control.
German patent No. 29 09 504 discloses a pressure control valve wherein the valve tappet is configured as a slide valve for pressure control in order to provide a pressure fluid connection between a first and a second pressure fluid port in a first switch position and to separate the above-mentioned pressure fluid ports in a second switch position of the valve slide. In the third switch position, the valve tappet will open a spherical non-return valve, thereby opening another pressure fluid connection to the second pressure fluid port.
However, a shortcoming of the pressure control valve is that the valve slide, on the one hand, necessitates a high degree of fitting precision to be able to govern leakage flows at the control edge which are responsive to manufacture and temperature. On the other hand, no provision is made to ensure the pressure reduction in the connected line system in case the valve slide becomes jammed.
European patent No. 0 353 635 discloses a valve assembly having a slide valve which acts as a flow control valve. The flow control valve generally has a piston which controls the volume flow between a pressure fluid source and a pressure fluid consumer as a function of the switch position of an electromagnetically operated actuating member. To perform this function, the piston has a relatively long stem with through-bores which include control edges. The control edges cover the pressure fluid channels of the pressure fluid consumer or the pressure fluid source which open radially into the valve housing. Undesired leakage due to the annular slot in the area of the control edge cannot be prevented in spite of the relatively long piston stem. Further, the serial arrangement of the flow control valve and the electromagnetically operable actuating member causes a substantial structural volume of the valve assembly. Sealing problems which are typical of slide valves will occur.